Clinical Study On The Effect Of Norepinephrine On Venous Return In Mechanically Ventilated Patients With Septic Shock

Objective:To investigate the effects of norepinephrine on venous return in mechanically ventilated patients with septic shock.Methods:This study was a single-center prospective cohort study included in the EICU of the first affiliated hospital of Kunming medical university from January 201 8 to January 2020,which met the inclusion criteria.After full liquid resuscitation,Central Venous Pressure(CVP)reached 8cmH20,but Mean Arterial Pressure(MAP)for patients with septic shock mechanical ventilation who were still below 65mmHg,the patient’s name,gender,age,height,weight,basic diseases and other general information were recorded,as well as the APACHE score SOFA score.According to the 2016 guidelines for the campaign to save sepsis[1].The use of norepinephrine was recorded to record the Systemic Vascular Resistance Index of the patients after the use of norepinephrine.According to the standard of SVRI,norepinephrine dose was used in the NE1 group(<0.5ug/kg.min-1),NE2 group(0.5-lug/kg.min-1),NE3 group(1-1.5ug/kg.min-1),NE4 group(1.5-2ug/kg.min-1),and NE5(>2 ug/kg-min-1).Five groups of the differences in hemodynamic parameters were compared among each group,and the effects of different doses of norepinephrine on venous return were analyzed.Results:A total of 58 patients were included in the study,including 31 males(53.44%)and 27 females(46.56%).There were 11 people in NE1 group(<0.5ug/kg.min-1),13 people in NE2 group(0.5-lug/kg.min-1),11 people in NE3 group(1-1.5ug/kg.min-1),12 people in NE4 group(1.5-2ug/kg.min-1),and 11 people in NE5 group(>2ug/kg.min-1).Hemodynamic indexes(Pmsf,Pmsf-CVP,CVP,RVR,CO/VR)were different among each group,and the differences were statistically significant(P<0.05).With the increase of norepinephrine dose,Pmsf increased from 25.91±3.65mmHg in NE1 group to 66.76±2.75mmHg in NE4 group(P<0.05),and decreased from 66.76±2.75mmHg in NE4 group to 57.00±3.53mmHg in NE5 group(P<0.05).CVP increased from 12.36±3.07mmHg in NE1 group to 25.21±7.30mmHg in NE4 group(P<0.05),and decreased from 25.21±7.30mmHg in NE4 group to 20.85±3.48mmHg in NE5 group(P<0.05).Pmsf-CVP increased from 13.61±4.14mmHg in NE1 group to 42.09±7.44mmHg in NE4 group(P<0.05),and decreased from 42.09±7.44mmHg in NE4 group to 36.15±4.73mmHg in NE5 group(P<0.05).RVR increased from 2.00±0.88 mmHg.min/L in NE1 group to 10.27±0.71 mmHg.min/L in NE4 group(P<0.05),and decreased from 10.27±0.71 mmHg.min/L in NE4 group to 9.59±0.56 mmHg.min/L in NE5 group(P<0.05).CO/VR increased from 4.70±2.36L/min in NE1 group to 5.30±1.03L/min in NE2 group(P<0.05),decreased from 5.30±1.03L/min in NE2 group to 3.78±0.46L/min in NE3 group(P<0.05),and decreased to 3.59±0.80 L/min in NE4 group(P<0.05).There was no statistically significant difference between 3.59±0.80 L/min in NE4 group and 3.59±1.14 L/min in NE5 group(P>0.05).It is worth noting that MAP and SVRI did not change significantly with the increase of norepinephrine dose(P=0.619,P=0.997).When norepinephrine dose was increased in the range of less than 1 ug/kg.min-1,the increase of upstream pressure and pressure gradient of venous return exceeded the increase of venous return resistance,and venous return increased.However,when the norepinephrine dose was greater than 1 ug/kg.min-1 range,the resistance to venous return increased significantly(P<0.05),which exceeded the upstream pressure of venous return and the pressure gradient of venous return,resulting in decreased venous return and decreased cardiac output(P<0.05).In norepinephrine dose>2 ug/kg.min-1 range increase dosage,venous return upstream pressure,venous return pressure gradient and degree of venous return resistance are less than 1-2 ug/kg.min-1 within the scope of the extent of the increase(P<0.05),but the degree of venous return resistance is still more than venous return pressure gradient increase,eventually venous return reduced(P<0.05);Norepinephrine dose of 1.5-2 ug/kg.min-1 and greater than 2 ug/kg.min-1 had no significant difference in the effect on venous return(P>0.05).Conclusions:1.In patients with septic shock mechanical ventilation,when norepinephrine dose was less than 1 ug/kg.min-1,venous return increased with the increase of norepinephrine dose.2.In patients with septic shock mechanical ventilation,when the dosage of norepinephrine exceeded 1 ug/kg.min-1,venous return decreased.3.In mechanically ventilated patients with septic shock,the reduction of venous return did not increase further when the dosage of norepinephrine exceeded 1.5 ug/kg.min-1.